Cotton harvesters with row units include a number of picking units for harvesting cotton. Each picking unit includes at least one drum, and on some units there may be a front drum and a rear drum. In any event, on each drum there is a number of picker bars and on each picker bar there are a plurality of spindles. Each spindle can be tapered and have a barbed surface for removing the cotton from the cotton plant. Each row unit includes a doffer column having a plurality of doffers for removing picked cotton from the spindles. A doffer is a disc that may be coated in rubber or urethane and rotatably driven at a velocity greater than that of the spindles. In a conventional cotton harvester row unit, the spindles move underneath the bottom face of the doffers so that the cotton is unwrapped and stripped from the spindles.
In a conventional cotton picker row unit, there is a single gearbox input for rotatably driving all of the components of the row unit (i.e., the drum, spindles and doffers). During operation, drum speed is synchronized with the ground speed of the machine such that as the machine speed increases, the drum speed increases and vice versa. In many applications, the relationship between ground speed and drum speed is linear. Speed sensors and the like detect or measure ground speed of the machine, and the single gearbox input is controlled accordingly so that drum speed is synchronized to the ground speed. In doing so, the drum rotates when the machine is moving, and the drum is held from rotating when the machine is idle. Likewise, as the drum is rotatably driven, the spindles and doffers are also driven in a similar manner.
In this conventional system, however, the spindle speed is operably controlled in accordance with drum speed. Thus, as the drum speed decreases to match ground speed of the machine, the spindle speed also decreases. In certain situations, the load conditions on the drive system reach a maximum load condition, whereby the drive system cannot adequately power all of the components of the cotton harvester. In conventional drive systems, the speed of the cotton harvester must be reduced during a maximum load condition since there is a single gearbox input driving the drum and spindles together. Thus, there is a need in certain applications to be able to operably control drum speed and spindle speed independently from one another to modify power distribution when a maximum load condition is approached.